Electrical shorting block with captured spring-biased shorting connectors

ABSTRACT

An electrical shorting block has a molded body with a plurality of side-by-side recesses in which terminal members having first, tapped apertures are secured. A shorting bar supported in the molded body extends across but is spaced from the terminal numbers and has second apertures aligned with the first apertures. For the hot side terminal members, shorting connectors slidable through but captured by the apertures in the shorting bar have threaded ends which can be selectively threaded into the tapped first apertures of those terminal members. Helical compression springs bias the captured shorting connectors away from the terminal members when not used to short the terminal. Common terminal members are connected to the shorting bar by shorting screws which remain threaded into the first apertures. The terminal members preferably have both screw terminations and male fast-on terminations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrical terminations and particularly toshorting blocks for providing a short in an electrical circuit, such as,for instance, in the circuits for current transformers and especiallycurrent transformers used in electric power distribution systems.

2. Background Information

There are applications where it is necessary to provide a short in anelectrical circuit. One such application is in connection with currenttransformers in electric power distribution systems. If the load isremoved from a current transformer which remains coupled to an activepower circuit, the voltage in the secondary winding of the transformerwill soar and can result in damage. Accordingly, shorting blocks areused to provide a path for the current in the secondary winding tocirculate.

A known type of shorting block has an elongated molded body with anumber of flat terminal strips extending transversely with insulatingpartitions between them. The short, flat terminal strips have screwterminations at each end. A shorting bar extends longitudinally alongthe molded body across all the terminal strips and is secured as byscrews on top of the partitions. Shorting screws are passed throughapertures in the shorting block to engage threaded apertures in theterminal strips for those terminals which are to be shorted. When not inuse, the shorting screws have to be stored elsewhere. In one version ofthis known shorting block, a limited number of the shorting screws notbeing used are stored in blind apertures molded into flanges on the endsof the housing. These flanges also have mounting holes for securing theterminal block to a support. Thus, the termination and the shortingscrews all extend 180° from the mounting surface.

There is a need for improved electrical shorting blocks.

There is a special need for improved electrical shorting blocks in whichthe shorting connectors are not likely to be misplaced when not in use.There is an additional need for such an improved electrical shortingblock in which the unused shorting connectors are positively restrainedfrom creating an inadvertent short circuit.

SUMMARY OF THE INVENTION

These needs and others are satisfied by the invention which is directedto an electrical shorting block which includes a molded, electricallyinsulative body with a plurality of side-by-side recesses, and aterminal member in each recess having a first aperture. A shorting baris supported in the molded body extending across and spaced from theterminal members. This shorting bar has second apertures each alignedwith a first aperture in one of the terminal members. Shortingconnectors extend through one of the first and second apertures forengagement with the other. Biasing means bias certain of the shortingconnectors out of such engagement. Preferably, the certain shortingconnectors are slidable through but captured by the apertures in theshorting bar and are extendable for selected engagement with the firstapertures in the terminal members.

Preferably, the certain shorting connectors are shorting screws havingan elongated shaft with a head at one end and a threaded section onlyadjacent a second end. The spring is a helical compression springbetween the head and the shorting bar which biases the threaded sectionagainst the shorting bar. The apertures in the shorting bar for thesecertain shorting screws is also threaded to form a stop. The shortingblock of the invention provides a convenient means of stowing theshorting screws used to selectively short certain of the terminationswhile also providing a clear visual indication as to which of theterminations are shorted. Additional details of the novel shorting blockare specified in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the invention can be gained from the followingdescription of the preferred embodiments when read in conjunction withthe accompanying drawings in which:

FIG. 1 is an exploded isometric view of a terminal block in accordancewith the invention with some parts eliminated for clarity.

FIG. 2 is an isometric view of an assembled terminal block in accordancewith the invention.

FIG. 3 is a rear isometric view of the terminal block.

FIG. 4 is an exploded isometric view of a terminal member which formspart of the shorting block of the invention.

FIG. 5 is a vertical sectional view taken along the line 5--5 in FIG. 2.

FIG. 6 is a cross sectional view taken along the line 6--6 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is directed to a shorting block particularly suitable as asecondary termination shorting block for electric power distributionsystems; however, it will be understood by those skilled in the art thatthe terminal block has other additional applications.

Referring particularly to FIGS. 1 and 2, the shorting block 1 of theinvention has a molded body 3 made of an electrically insulativematerial. The molded body 3 has side-by-side elongated recesses 5 formedin a front face 7 by integral partitions 9. As best seen in FIGS. 5 and6, the molded body 3 has thin walled sections 11 between the partitions9 which form the recesses 5. First slots 13 extending transverselyacross the recesses 5 are formed in forwardly extending projections 15of the thin walled sections as best seen in FIG. 1, half cylindricalgrooves 17 extend through the projections 15 perpendicular to the slots13.

The thin walled sections 11 of the molded body 3 also form an outwardlyfacing shoulder 19 in each recess. Second slots 21 are formed in each ofthe shoulders 19. A forwardly projecting tab 23 is molded below each ofthe second slots 21. The thin walled sections 11 of the body 3 alsoinclude a vertical wall section 25 below and recessed inward from theshoulder 19. Below this wall section 25 is a downwardly and rearwardlyextending wall section 27.

The thin walled sections 11 also include a back wall 29 extending upwardbeyond the projections 15 and terminates in a flange 31 which projectsforwardly and extends across all of the recesses 5. A recess 33 extendsalong the top of this flange 31 and leads to an undercut groove 35 whichextends around the ends of the recess. In every other recess 5, aU-shaped slot 37 extends through the flange 31. In the other recesses 5an arcuate shaped guide 39 is molded below the flange 31. These recesseshave an additional guide flange 41 with an arcuate cut-out 43 as seen inFIG. 6.

The molded body 3 of the mounting block 1 is configured for mounting ina mounting opening 45 in a mounting panel 47 as shown in FIGS. 5 and 6.The rear mounting face 48 of the molded body 3 has at each end a pair offixed upwardly directed mounting tabs 49 as seen in FIGS. 3, 5 and 6spaced from the back wall 29. In addition, flexible cantilevered catches51 with chamfered hooks 53 at their ends are integrally formed along thebottom of the wall 27. Two additional flexible cantilevered catches 55with chamfered hooks 57 on their ends project laterally outward from theends of the molded body. The molded body 3 is mounted in the mountingopening 45 by inserting the fixed mounting tabs 49 through the mountingopening 45 to engage the mounting panel 47 and then rotating the bottomof the molded housing inward toward the mounting panel so that thecantilevered catches 51,55 are deflected by the engagement of thechamfered hooks 53,57 on the edge of the opening 45. When the hooks passthrough the opening 45, the cantilevered catches 51,55 spring outward toengage the hooks 53,57 and firmly retain the molded body 3 to themounting panel 47.

The terminal block 1 of the invention further includes a terminal member59 seated in each of the recesses 5. The terminal members 59 comprise aconductive strip 61, which as best seen in FIG. 4 has a first section 63extending from one end 65 and a second section 67 extending from asecond end 69. The first section 63 of the conductor strip 61 has afirst tapped aperture 71. A middle section 73 of the conductive strip 61has a tapped aperture 75 which receives a terminal screw 77 carrying aclamping plate 79 to form a screw termination 81. The first section 63of the conductive strip 61 is substantially perpendicular to the secondsection 67 with the middle section 73 between them forming a small anglewith the first section for a purpose to be explained further. The secondsection 67 of the conductive strip 61 forms adjacent the end 69 aFASTON® male stab type termination 83. A barbed mounting tab 85 ispunched out of the second section. In addition, mounting barbs 87 arepunched out of the first section 63 of the conductive strip 61. In someapplications, all of the terminal members 59 need not have male FASTON®terminations. In such cases, those terminal members 59 only have thefirst section 63 and middle section 73 and are retained in place in therecesses 5 by the barbs 87.

The terminal members are secured in the recesses 5 and the molded body 3by inserting the first end 65 of the conductive strip 61 into the firstslot 13. The conductive strip 61 is then rotated downward so that themounting tab, guided by the guide tab 23 enters the second slot 21. Asshown in FIGS. 5 and 6, with the second section 67 of the conductivestrip 61 seated against the shoulder 19, the male FASTON® termination 83projects downwardly and is spaced from the vertical wall section 25 toprovide clearance for the attachment of a female fast-on termination(not shown).

The shorting block 1 also includes a shorting bar 89 which seats in therecess 33 in the molded housing and has barbs 91 which engage the groove35. This shorting bar 89 has second apertures 93 which are aligned withthe first apertures 71 in the terminal members 59 as can be seen fromFIGS. 5 and 6. Every other ones of the second apertures 93' which arealigned with the recesses 5' are punched to form retaining lances 94.

The shorting block 1 further includes shorting connectors in the form ofshorting screws 95 and 97. The shorting screws 95 extend through theuntapped second apertures 93 and engage the first tapped apertures 71 inthe terminal members 59 mounted in the recesses 5. The shorting screws97 have an elongated shaft 99 having threads 101 only on the free end.The shorting screws 97 are pushed through the retaining lances 94 in thesecond apertures 93' and engage the first apertures 71 in the terminalmembers 59. Helical compression springs 103 are seated between theshorting bar and heads 105 on the shorting screws 97. The arcuate guides39 and guide flanges 41, help to align the shorting screws 97 with thecorresponding first aperture 71 in the terminal members 59. The halfcylindrical groove 17 in the projections 15 allow clearance for theshorting screws 95 and 97.

As mentioned, the shorting block of the invention is particularly usefulin providing terminations for current transformers such as are used inelectric power distribution systems. In such an application, terminalmembers 59 in adjacent recesses 5 and 5' are paired for connection tothe secondary windings of a current transformer (CT). For a three-phasesystem having three current transformers, this would require sixterminal members. The common side of the respective CT secondaries areconnected through leads with female fast-on terminations (not shown) tothe male fast-on termination 83 of the terminal member 59 in thecorresponding recess 5. The shorting screws 95 in the recesses 5 engagethe first apertures 71 in the corresponding terminal members so thatthese terminal members are all electrically connected to the shortingbar 89. As there are seven terminal members 59 in the shorting block 1,there is one remaining which is in a recess 5 connected to the shortingbar by a corresponding shorting screw 95. This seventh terminalconnector is connected through its male FASTON® termination 83 and alead with a female FASTON® termination (not shown) to ground. The malefast-on terminations 83 of the other terminal members 59 of each pair ofterminal members are connected through leads, again with female FASTON®terminations (not shown), to the hot side of the CT secondary. A loaddevice (not shown) is connected to each pair of terminal members throughthe screw termination 81, thereby providing a circuit for circulation ofCT secondary current.

As has been discussed, it is imperative that a circuit be maintained forcirculation of secondary current in a current transformer in which theprimary winding remains coupled to a source. If the corresponding loaddevice is removed for service or the circuit is interrupted for someother reason, the shorting screw 97 is screwed into the correspondingfirst aperture 71 of the hot terminal member 59 to complete the circuitfor the secondary winding of that current transformer through theshorting bar 89. However, as long as a circuit is completed between thescrew terminations 81 of a pair of terminal members connected to thesecondary winding of a current transformer, the corresponding shortingscrew 97 is not needed. In that case, it is unscrewed from the terminalmember and biased upward away from the corresponding terminal member 59by the spring 103. The retaining lances 94 in the aperture 93' providesan upward stop for the shorting screw 97. Thus, the shorting screw 97 iscaptured in an inoperative position but is readily available forre-engagement. This arrangement also provides a quick visual referenceas to which pairs of terminal members are shorted. As can be seen fromFIG. 2, the shorting block 1 also provides convenient access to the malefast-on terminations and screw terminations from the front face of theterminal block if these terminations are essentially 90° with respect toeach other. Clearly, it will be appreciated that terminal blocks withother numbers of terminal members can be realized in accordance with theinvention.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of invention which is to be given the fullbreadth of the claims appended and all equivalents thereof.

What is claimed is:
 1. An electrical shorting block comprising:a moldedelectrically insulative body having a plurality of side-by-siderecesses; a terminal member in each recess each having a first aperture;a shorting bar supported in said molded body extending across and spacedfrom said terminal members and having second apertures each aligned witha first aperture in one of said terminal members; shorting connectorsextending through one of said first and second apertures for eachterminal member for selected engagement with the other of said first andsecond apertures; and biasing means biasing certain of said shortingconnectors out of engagement with said other of said first and secondapertures.
 2. The electrical shorting block of claim 1 wherein saidterminal members further have a screw termination.
 3. The electricalshorting block of claim 2 wherein said terminal members further have amale stab type termination.
 4. The electrical terminal block of claim 1wherein said terminal members have a male stab type termination.
 5. Theelectrical switching block of claim 1 wherein said other of said firstand second apertures are threaded and said certain of said shortingconnectors each comprises an elongated shaft, a head on one end of saidelongated shaft and a threaded section only adjacent a second end ofsaid elongated shaft, said biasing means comprising a helicalcompression spring between said head and said one of said first andsecond apertures.
 6. The electrical shorting block of claim 5 whereinsaid threaded section of said elongated shaft of said certain shortingconnectors is only long enough to engage one of said first and secondapertures at a time.
 7. The electrical shorting block of claim 5 whereinsaid molded electrically insulative body has guides between saidshorting bar and said terminal members for guiding said elongated shaftsof said shorting connectors to align said threaded sections with threadsin said other apertures.
 8. The electrical shorting block of claim 5wherein said one of said first and second apertures comprises saidsecond apertures in said shorting bar and said other of said first andsecond apertures comprises said first apertures in said terminalmembers.
 9. The electrical shorting block of claim 1 wherein saidterminal members are conductive strips having first sections including afirst end of said conductive strip, a second section extending from asecond end of said conductive strip and a middle section between saidfirst section and said second section, said first apertures beinglocated in said first sections of said conductive strips, andterminations in at least one section of said conductive strip.
 10. Theelectrical shorting block of claim 9 wherein said terminations comprisescrew terminations in said middle sections of said conductive strips andmale stab type terminations forming said second ends of said secondsections of said conductive strips.
 11. The electrical shorting block ofclaim 10 wherein said molded electrically insulative body has firstslots in said recesses in which first ends of said conductive strips areretained.
 12. The electrical shorting block of claim 11 wherein saidsecond section of said conductive strip extends at an angle of about 90°to said first section.
 13. The electrical shorting block of claim 12wherein said second sections of said conductive strips have tabsextending transversely therefrom and said molded body has second slotsin said recesses in which said tabs are retained.
 14. The electricalshorting block of claim 13 wherein said molded body has additionalguides in said recesses guiding said tabs into said second slots. 15.The electrical shorting block of claim 12 wherein said molded body has amounting surface about 90° to said first sections of said conductivestrips.
 16. The electrical shorting block of claim 10 wherein said oneapertures are said second apertures in said shorting bar and said otherapertures are said first apertures in said conductive strips and arethreaded, said shorting connector comprising an elongated shaft, a headat one end of said elongated shaft and a threaded section only adjacentthe other end of said elongated shaft, and said biasing means compriseshelical compression springs between said heads and said shorting bars.17. The electrical shorting block of claim 15 wherein said firstsections of said conductive strips are planar so that said elongatedshafts of said shorting connectors are substantially parallel to screwsof said screw terminations.
 18. The electrical shorting block of claim 1adapted for mounting in a mounting opening in a mounting panel whereinsaid molded electrically insulative body has a mounting surface,integral cantilevered catches adjacent said mounting surface forengaging said mounting opening and integral mounting stops spaced fromand facing said catches to engage edges of said mounting opening. 19.The electrical shorting block of claim 18 wherein said molded body hasat least two cantilevered catches 90° to each other.
 20. The electricalshorting block of claim 18 wherein said mounting surface issubstantially parallel to said shorting connectors.
 21. An electricalshorting block comprising:a molded body having a plurality ofside-by-side recesses; a terminal member in each recess each having afirst aperture; a shorting bar supported in said molded body extendingacross and spaced from said terminal members and having second apertureseach aligned with a first aperture in one of said terminal members; andshorting means comprising shorting connectors slidable through butcaptured by said second apertures in said shorting bar and extendablefor selected engagement with said first apertures in said terminalmembers.
 22. The electrical shorting block of claim 21 wherein saidshorting means further including springs biasing said shortingconnectors away from said terminal members.